The door to the chamber of secrets has opened a crack, as a bibliography of JK Rowling’s work reveals insider details about the publication of her bestselling Harry Potter series, shedding light on why extensive edits to the Prisoner of Azkaban left the author “sick” of the novel, and how the manuscript of The Order of the Phoenix was handed over in a London pub, concealed in a plastic bag.

Author and Sotheby’s director for children’s books Philip Errington has spent five years compiling the 544-page JK Rowling: A Bibliography 1997-2013, a work described as “slavishly thorough and somewhat mind-boggling” by Rowling which has just been published by Bloomsbury Academic. As well as providing complete bibliographic details of each edition of all Rowling’s books to date, in order to “record fact and dispel rumour” – and enable fans to work out if they might have a rare edition – Errington has also dug through Bloomsbury’s archives and interviewed its staff to include detailed information on the publishing history of Rowling’s books.

“Finally! I’ve read this book so much I’m sick of it, I never read either of the others over and over again when editing them, but I really had to this time,” writes Rowling in an undated letter to her editor Emma Matthewson about the Prisoner of Azkaban, quoted by Errington in his book. “If you think it needs more work, I’m willing and able, but I do think this draft represents an improvement on the first; the dementors are much more of a presence this time round, I think,” she adds.

Matthewson replies in August 1998, calling it “just great Jo – quite a huge, teetering tottering plot that never quite falls down! What a feat!” But the edits clearly continued, with Rowling writing to her editor in November that year: “An annoying little speech bubble has just popped onto my screen saying ‘looks like you’re writing a letter. Would you like some help?’ This laptop is too clever for its own good … I am so sick of re-reading this one that I’ll be hard put to smile when it comes to doing public readings from it. But perhaps the feeling will have worn off by next summer… ”

She had been less troubled by the changes which were made to the Chamber of Secrets in 1997, Errington reveals; after Matthewson told Rowling the work was “absolutely brilliant”, adding “generally, as we’ve discussed, the manuscript is over-long”, Rowling returns it in October, writing “I’ve done more to it than you suggested, but I am very happy with it now, which wasn’t the case before. The hard work, the significant rewrites I wanted to do, are over, so if it needs more cuts after this, I’m ready to make them, speedily… ”

One of the casualties, notes Errington, was a song for the ghost Nearly Headless Nick – a loss Rowling described as a “wrench”, while admitting it was “superfluous to requirements”. It has since appeared online after the author posted it on her website.

Errington also reveals Rowling’s alternative suggestions for a title to Harry Potter and the Goblet of Fire – Harry Potter and the Death Eaters, Harry Potter and the Fire Goblet and Harry Potter and the Three Champions; and following an interview with Bloomsbury chief executive Nigel Newton, the shenanigans which went on when Rowling’s then-agent Christopher Little wanted to pass on the finished manuscript of Harry Potter and the Order of the Phoenix.

Little summoned Newton to The Pelican pub in Fulham for a drink, he told Errington – Newton knew the meeting could be significant, as the location was where Little had delivered the previous book to Bloomsbury. “So I drove to The Pelican, a pub off the Fulham Road not far from Stamford Bridge, in a state of high alert. And I went in and there was a massive Sainsbury’s plastic carrier bag at this feet … he said nothing about that and I said nothing and he just said ‘Drink?’ and I said, ‘a pint, please’. So we stood at the bar and drank our pints and said nothing about Harry Potter. But when we left I walked out with the carrier bag. It was a classic dead letter drop,” said Newton.

“So I put this bag into the back of my car and drove it home. By this stage the series was so enormous that I was almost frightened to be in physical possession of it … I shoved it under the bed. I had another typescript sitting there … so I stuffed [the] top four pages of David Guterson’s East of the Mountains on the top and then stayed up all night reading it, which my wife did find a bit odd … There was no question of showing any of it to her. Even then I was putting bits of it in the safe.”

Also recording that the auction record to date for a first edition of Harry Potter and the Philosophers’ Stone is £150,000, and that the New York Times listed Harry Potter and the Sorcerer’s Stone in its bestseller lists describing the plot as one about “a Scottish boy”, Bloomsbury Academic describes Errington’s work a the “definitive bibliography” of Rowling’s writings to date.

“There is a lot of incorrect information out there and this is a chance to set the record straight with detailed research,” said Errington. “I’m very fortunate that Bloomsbury let me into their archives, and that I was able to interview key people. This could act as a map for the future … you can see how the Harry Potter series just took off.”